Exposure apparatus, and device manufacturing method

ABSTRACT

A lithographic projection apparatus includes a substrate table that holds a substrate, a projection system that projects a patterned beam of radiation onto the substrate, and a liquid confinement structure that confines a liquid in a space between the projection system and the substrate, the substrate, the substrate table, or both, to form a part of a boundary of the space. In addition, a closing plate forms a part of a boundary of the space in place of the substrate, the substrate table, or both, when moved without substantially disturbing the liquid, the liquid confinement structure, or both.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 11/258,846filed Oct. 27, 2005, which in turn is a continuation of InternationalApplication PCT/JP2004/008595, with an international filing date of Jun.18, 2004. The disclosures of these applications are hereby incorporatedherein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to exposure apparatus, and devicemanufacturing methods, and more particularly to an exposure apparatusused in a lithography process where electronic devices such assemiconductor devices, liquid crystal display devices, or the like ismanufactured, and a device manufacturing method that uses the exposureapparatus.

2. Description of the Related Art

In a lithography process for producing electronic devices such assemiconductor devices (integrated circuits), liquid crystal displaydevices, or the like, projection exposure apparatus are used thattransfer the image of a pattern formed on a mask or a reticle(hereinafter generally referred to as a ‘reticle’) via a projectionoptical system onto each of the shot areas of a photosensitive substrate(hereinafter referred to as a ‘substrate’ or a ‘wafer’) such as a wafer,a glass plate, or the like whose surface is coated with a resist(photosensitive agent). As this type of projection exposure apparatus,conventionally, a reduction projection exposure apparatus by astep-and-repeat method (the so-called stepper) has been frequently used.However, recently, a projection exposure apparatus by a step-and-scanmethod (the so-called scanning stepper) that performs exposure bysynchronously scanning the reticle and the wafer is also gatheringattention.

The resolution of the projection optical system equipped in the exposureapparatus becomes higher when the wavelength (hereinafter also referredto as ‘exposure wavelength’) of the exposure light used becomes shorter,or when the numerical aperture (NA) of the projection optical systembecomes larger. Therefore, the exposure wavelength used in theprojection exposure apparatus is becoming shorter each year due to finerintegrated circuits, along with the increase in the numerical apertureof the projection optical system. The exposure wavelength currentlymainly used is 248 nm of the KrF excimer laser, however, a shorterwavelength of 193 nm of the ArF excimer laser has also been put topractical use.

In addition, along with resolution, depth of focus (DOF) is alsoimportant when exposure is performed.

Resolution R and depth of focus δ can be expressed as in the equationsbelow.R=k ₁ ·λ/NA  (1)δ=k ₂ ·λ/NA ²  (2)

In this case, λ is the exposure wavelength, NA is the numerical apertureof the projection optical system, and k₁ and k₂ are processcoefficients. From equations (1) and (2), it can be seen that whenexposure wavelength λ is shortened and numerical aperture NA is enlarged(increased NA) to increase resolution, depth of focus δ becomes narrow.In a projection exposure apparatus, when exposure is performed, anauto-focus method is used to make the surface of the wafer match theimage plane of the projection optical system. Accordingly, it isdesirable for depth of focus δ to have a certain amount of width.Therefore, methods have been proposed in the past to substantially widenthe depth of focus, such as the phase shift reticle method, the modifiedillumination method, the multi-layer resist method, and the like.

As is described above, in the conventional projection exposureapparatus, the depth of focus is becoming narrow due to the shorterexposure wavelength and the increased numerical aperture. And, in orderto cope with higher integration, the exposure wavelength is presumed tobe shorter in the future. If such a situation continues, the depth offocus may become so small that margin shortage may occur during theexposure operation.

Therefore, as a method of substantially shortening the exposurewavelength while increasing (widening) the depth of focus when comparedwith the depth of focus in the air, an immersion exposure method(hereinafter also appropriately referred to as ‘immersion method’) hasbeen proposed. In the immersion method, resolution is improved byfilling the space between the end surface of the projection opticalsystem and the wafer surface with liquid such as water or an organicsolvent to make use of the fact that the wavelength of the exposurelight in the liquid becomes 1/n of the wavelength in the air (n is therefractive index of the liquid which is normally around 1.2 to 1.6). Inaddition, in the immersion method, the depth of focus is substantiallyincreased n times when compared with the case where the same resolutionis obtained by a projection optical system (supposing that such aprojection optical system can be made) that does not employ theimmersion method. That is, the depth of focus is substantially increasedn times than that in the air.

However, in the case the immersion method above is merely applied to aprojection exposure apparatus by the step-and-repeat method, the liquidspills from the space between the projection optical system and thewafer when the wafer is moved in between shots by a step movement to theexposure position for the next shot area after exposure of a shot areahas been completed. Therefore, the liquid has to be supplied again, andthe recovery of the liquid could also be difficult. In addition, in thecase when the immersion method is applied to a projection exposureapparatus by the step-and-scan method, because exposure is performedwhile moving the wafer, the liquid has to be filled in the space betweenthe projection optical system and the wafer while the wafer is beingmoved.

Considering such points, a proposal has been recently made on ‘aninvention related to a projection exposure method and a unit where apredetermined liquid flows along the moving direction of a substrate, sothat the liquid fills in the space between the end portion of an opticalelement on the substrate side of a projection optical system and thesurface of the substrate when the substrate is moved in a predetermineddirection,’ (for example, refer to patent document 1 below).

Besides such a proposal, as a proposal for improving resolution as inthe immersion exposure method, a lithography system is known that placesa solid immersion lens in the section between a projection lithographylens system (projection optical system) and a sample (for example, referto patent document 2 below).

According to the invention disclosed in patent document 1 below,exposure with high resolution and a larger depth of focus than the depthof focus in the air can be performed by the immersion method, and theliquid can also be filled in the space between projection optical systemand the substrate in a stable manner, or in other words, can be held,even when the projection optical system and the wafer relatively moves.

However, in the invention disclosed in patent document 1 below, becausethe supply piping, the recovery piping, and the like are arrangedoutside the projection optical system, the degree of freedom is limitedfor peripherals such as sensors of various kinds like a focus sensor oran alignment sensor that have to be arranged around the projectionoptical system.

In addition, in the invention according to patent document 1 below, inthe case there is a flow in the liquid filled in the space between theprojection optical system and the substrate, when the liquid isirradiated by the exposure light on exposure, temperature inclination orpressure inclination relative to the direction of the flow may occurwithin the projection area of the pattern in the space between theprojection optical system and the substrate. Especially when the spacein between the projection optical system and the substrate is large, orin other words, the layer of liquid is thick, such temperatureinclination or pressure inclination could be the cause of aberrationsuch as inclination of image plane, which could lead to partialdeterioration in the transfer accuracy of the pattern, which in turncould be the cause of deterioration in the line width uniformity of thetransferred image of the pattern. Accordingly, the layer of liquid ispreferably thin. However, in this case, the space in between theprojection optical system and the substrate becomes narrow, which makesit difficult to arrange a focus sensor.

In addition, in the invention according to patent document 1 below, itis difficult to recover the liquid completely, and the probability washigh for the liquid used for immersion to remain on the wafer afterexposure. In such a case, temperature distribution in the atmosphere ora refractive index change in the atmosphere occurs by the heat ofvaporization generated when the remaining liquid evaporates, and thesephenomena could be the cause of measurement errors in a laserinterferometer system that measures the position of the stage on whichthe wafer is mounted. Furthermore, the remaining liquid on the wafercould move to the back of the wafer, which could make the wafer stick tothe carrier arm and difficult to separate.

Meanwhile, in the lithography system according to patent document 2below, the distance between the solid immersion lens (hereinaftershortened appropriately as ‘SIL’) and the sample is maintained at around50 nm or under. However, in the lithography system in the near futurewhose target is to transfer and form a fine pattern onto a sample (suchas a wafer) at a line width of around 70 nm or under, when an air layerwhose thickness is 50 nm exists between the SIL and the sample, itbecomes difficult to obtain sufficient resolution in the image of thefine pattern referred to above. That is, in order to obtain sufficientresolution in the fine pattern above, the distance between the SIL andthe sample has to be maintained at a maximum of 30 nm or under.

However, in the lithography system according to patent document 2 below,because a configuration using air bearings is employed to maintain thedistance between the SIL and the sample, it is difficult to obtainsufficient vibration damping due to the nature of air bearings. As aresult, the distance between the SIL and the sample could not bemaintained at 30 nm or under.

As is described, in the conventional examples disclosed in patentdocuments 1 and 2 below and the like, various points are found thatshould be improved.

Patent Document 1: the pamphlet of International Publication NumberWO99/49504

Patent Document 2: the description of U.S. Pat. No. 5,121,256

SUMMARY OF THE INVENTION

The present invention was made under such circumstances, and has as itsfirst object to provide an exposure apparatus that can transfer apattern onto a substrate almost free from defocus, without necessarilyhaving to arrange a focal position detection system.

In addition, the second object of the present invention is to provide anexposure apparatus suitable for the immersion method that has aplurality of tables.

In addition, the third object of the present invention is to provide adevice manufacturing method that can improve the productivity of highlyintegrated microdevices.

According to a first aspect of the present invention, there is provideda first exposure apparatus that illuminates a pattern with an energybeam and transfers the pattern onto a substrate via a projection opticalsystem, the exposure apparatus comprising: a table on which a substrateis mounted that can move two-dimensionally while holding the substrate;and a hydrostatic bearing unit arranged on an image plane side of theprojection optical system, the unit including at least one hydrostaticbearing that supplies liquid in a space between a bearing surface facingthe substrate mounted on the table and the substrate so as to maintainthe distance between the bearing surface and the surface of thesubstrate by static pressure of the liquid.

According to the exposure apparatus, the hydrostatic bearing unitmaintains the distance between the bearing surface of the hydrostaticbearing and the surface of the substrate in the direction of the opticalaxis of the projection optical system at a predetermined value. Unlikestatic gas bearings, hydrostatic bearings utilize the static pressure ofthe liquid supplied to the space between the bearing surface and thesupport object (substrate), which is an incompressible fluid, therefore,the rigidity of the bearings is high, and the distance between thebearing surface and the substrate can be maintained both stable andconstant. In addition, liquid (e.g., pure water) is higher in viscositythan gas (e.g., air) and is superior in vibration damping when comparedwith gas. Accordingly, with the exposure apparatus of the presentinvention, pattern transfer onto a substrate substantially free fromdefocus can be achieved, without necessarily having to arrange a focalposition detection system.

In this case, in a state where higher refractive index fluid than airconstantly exists in the space between the projection optical system andthe surface of the substrate, exposure of the substrate can be performedwith the energy beam via the pattern, the projection optical system, andthe high refractive index fluid. In such a case, because the substrateis exposed with the energy beam in a state where the higher refractiveindex fluid than air constantly exists in the space between theprojection optical system and the surface of the substrate, via thepattern, the projection optical system, and the high refractive indexfluid, the wavelength of the energy beam on the surface of the substratecan be shortened to 1/n^(th) of the wavelength in the air (n is therefractive index of the high refractive index fluid), and furthermore,the depth of focus is widened n times compared to the depth of focus inthe air.

In this case, the high refractive index fluid can be liquid.

In this case, liquid for the hydrostatic bearing can be used as the highrefractive index fluid to fill the space between the projection opticalsystem and the substrate on the table.

In the first exposure apparatus of the present invention, the at leastone hydrostatic bearing can be arranged in a state where a positionalrelation with the projection optical system is constantly maintained ina direction of an optical axis of the projection optical system.

In the first exposure apparatus of the present invention, an opticalmember closest to the substrate that constitutes the projection opticalsystem can have a curved surface on the pupil plane side and a planarsurface on the image plane side.

In this case, the planar surface on the image plane side of the opticalmember closest to the substrate constituting the projection opticalsystem can be substantially co-planar with the bearing surface of thehydrostatic bearing. In such a case, for example, it becomes possible tomaintain the distance between the optical member and the substrate ataround 10 μm. Especially when the space between the projection opticalsystem and the surface of the substrate is filled with the highrefractive index fluid, the amount of the high refractive index fluidconsumed will be extremely small, and the image forming quality of thepattern image will be less affected by the refractive index change(caused by temperature or the like) of the fluid. Further, especiallywhen the high refractive index fluid is liquid, it is advantageous whendrying the wafer.

In the first exposure apparatus of the present invention, thehydrostatic bearing unit can supply the liquid to a space between thebearing surface of the at least one hydrostatic bearing and thesubstrate, and can also drain liquid in the space between the bearingsurface and the substrate outside using negative pressure. In such acase, the hydrostatic bearing will have a higher rigidity, and canmaintain the distance between the bearing surface and the substrateconstantly with more stability.

In this case, the at least one hydrostatic bearing can be arranged in astate surrounding a projection area of the pattern on the substrate.

In this case, as the at least one hydrostatic bearing, a plurality ofhydrostatic bearings can be used, and the plurality of hydrostaticbearings can be arranged in a state surrounding the projection area ofthe pattern on the substrate, or the at least one hydrostatic bearingcan be a single bearing that has a bearing surface which surrounds theprojection area of the pattern on the substrate.

In the first exposure apparatus of the present invention, in the casethe at least one hydrostatic bearing is arranged in a state surroundingthe projection area of the pattern on the substrate, on the bearingsurface of the hydrostatic bearing, a plurality of ring-shaped groovescan be formed multiply, and the plurality of ring-shaped grooves cancontain at least one each of a liquid supply groove and a liquiddrainage groove.

In this case, the plurality of grooves can include a liquid supplygroove, and at least one each of a liquid drainage groove, the liquiddrainage grooves formed on both the outer and inner sides of the liquidsupply groove, respectively.

In the first exposure apparatus of the present invention, in the casethe at least one hydrostatic bearing is arranged in a state surroundingthe projection area of the pattern on the substrate, the exposureapparatus can further comprise: a gap sensor arranged in the hydrostaticbearing that measures the distance between the bearing and the surfaceof the substrate in at least one measurement point, wherein thehydrostatic bearing unit can adjust at least one of negative pressurefor draining the liquid and positive pressure for supplying the liquid,according to measurement values of the gap sensor.

In the first exposure apparatus of the present invention, the exposureapparatus can further comprise: at least one fluid static bearing thatis arranged facing the hydrostatic bearing via the table, the fluidstatic bearing supplying fluid to a space between a bearing surfacefacing the table and the table so that a gap between the bearing surfaceand a surface of the table can be maintained by static pressure of thefluid. In such a case, the table and the substrate on the table isconsequently held in the vertical direction by the hydrostatic bearingdescribed earlier and the fluid static bearing described above. In thiscase, for example, the distance between each of the bearing surfaces andthe substrate or the table can be maintained stable and constant ataround 10 μm or under. Accordingly, the table itself does not have tohave high rigidity, which makes it possible to reduce the thickness ofthe table, and also reduce its weight.

In this case, the fluid static bearing can be a single bearing that hasa bearing surface which surrounds an area corresponding to a projectionarea on the opposite side of a surface of the table where the substrateis mounted.

In this case, a plurality of annular grooves can be multiply formed onthe bearing surface of the fluid static bearing, the plurality ofgrooves containing at least one each of a fluid supply groove and afluid drainage groove.

In this case, the plurality of grooves can include a fluid supplygroove, and at least one each of a fluid drainage groove, the fluiddrainage grooves formed on both the outer and inner sides of the fluidsupply groove, respectively.

In the first exposure apparatus of the present invention, when theexposure apparatus comprises the fluid static bearing described above,the fluid can be liquid. More specifically, as the fluid static bearing,the hydrostatic bearing can be used. In such a case, the table and thesubstrate on the table is held in the vertical direction by the liquid,which is an incompressible fluid, therefore, the table and the substrateon the table can be held in a more stable manner. In this case, becausethe bearings above and below both have high rigidity, the distancebetween each of the bearing surfaces and the substrate or the table canbe maintained constant more stably.

In the first exposure apparatus of the present invention, the distancebetween the bearing surface and the surface of the substrate can bemaintained larger than zero and around 10 μm and under.

In the first exposure apparatus of the present invention, the exposureapparatus can further comprise: a position detection system that detectspositional information of the table within a plane where the table movestwo-dimensionally as is earlier described.

According to a second aspect of the present invention, there is provideda second exposure apparatus that supplies liquid in a space between aprojection optical system and a substrate, illuminates a pattern with anenergy beam, and transfers the pattern onto the substrate via theprojection optical system and the liquid, the exposure apparatuscomprising: a first table where a mount area of the substrate is formedand the surface of an area around the mount area is set substantiallyflush to the surface of a substrate mounted on the mount area, the firsttable being movable within an area of a predetermined range thatincludes a first area containing a position just below the projectionoptical system where the liquid is supplied and a second area on oneside of an axial direction of the first area; a second table whosesurface is set substantially flush to the surface of the substrate, thesecond table being movable independently from the first table within anarea including the first area and the second area; and a stage drivesystem that drives the first table and the second table, and also drivesthe first table and the second table simultaneously while maintaining astate that is both tables being close together or both tables being incontact in the axial direction, from the second area side toward thefirst area side in the axial direction on a transition from a firststate where one of the tables is positioned at the first area to asecond state where the other table is positioned at the first area.

According to the exposure apparatus, on a transition from a first statewhere one of the tables is positioned at the first area, which includesthe position just under the projection optical system where liquid issupplied, to a second state where the other table is positioned at thefirst area, the stage drive system drives the first table and the secondtable simultaneously in the axial direction from the second area sidetoward the first area side while maintaining a state where both tablesare close together or both tables are in contact in the axial direction.Therefore, one of the tables is constantly located just under theprojection optical system, and the state where an immersion area isformed in the space between the table (the substrate or the periphery ofthe area where the substrate is mounted) and the projection opticalsystem is maintained, which allows the liquid to be held in the spacebetween the projection optical system and the table and the liquid canbe kept from spilling.

In addition, in a lithographic process, by performing exposure using oneof the first and second exposure apparatus in the present invention, thepattern can be formed on the substrate with good accuracy, which allowsproduction of higher integrated microdevices with good yield.Accordingly, further from another aspect of the present invention, itcan be said that the present invention is a device manufacturing methodthat uses one of the first and second exposure apparatus in the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a view that schematically shows a configuration of an exposureapparatus in a first embodiment of the present invention.

FIG. 2 is a perspective view that shows a configuration of a drive unitwith a wafer table TB.

FIG. 3 is a view that schematically shows a sectional view of the driveunit in FIG. 2 in an XZ plane, with a piping system used to supply/drainliquid to hydrostatic pads.

FIG. 4 is a bottom surface view of a hydrostatic pad 32.

FIG. 5 is a view that shows a flow of water around hydrostatic pads 32and 34, in the case the hydrostatic pads support a wafer table.

FIG. 6 is a block diagram that shows a partly omitted configuration of acontrol system, which is employed in the exposure apparatus in the firstembodiment.

FIG. 7 is a view that shows a configuration of a wafer table in the casean interferometer is used as a position detection system.

FIG. 8 is a view used to describe a modified example.

FIG. 9 is a planar view that shows a configuration related to a waferstage unit, which constitutes an exposure apparatus in a secondembodiment.

FIG. 10 is a view used to describe an operation of wafer table exchangein the second embodiment.

FIG. 11A is a view used to describe a modified example of a hydrostaticpad.

FIG. 11B is a view that shows a water supply piping (and a waterdrainage piping) that can be suitably used in the hydrostatic pad inFIG. 11A.

FIG. 12 is a flow chart used to explain an embodiment of a devicemanufacturing method according to the present invention.

FIG. 13 is a flow chart that shows a concrete example related to step204 in FIG. 12.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

A first embodiment of the present invention will be described below,referring to FIGS. 1 to 6.

FIG. 1 shows the entire configuration of an exposure apparatus 100related to the first embodiment. Exposure apparatus 100 is a projectionexposure apparatus (the so-called scanning stepper) by the step-and-scanmethod. Exposure apparatus 100 is equipped with: an illumination system10; a reticle stage RST that holds a reticle R serving as a mask; anoptical unit PU; a wafer table TB that serves as a table on which awafer W serving as a substrate is mounted; a main controller 20 that hasoverall control over the entire apparatus, and the like.

As is disclosed in, for example, Kokai (Japanese Unexamined PatentPublication) No. 2001-313250 and its corresponding U.S. PatentApplication Publication No. 2003/0025890, illumination system 10 has anarrangement that includes parts such as a light source, an illuminanceuniformity optical system that includes an optical integrator or thelike, a beam splitter, a relay lens, a variable ND filter, a reticleblind (none of which are shown), and the like. Besides such anarrangement, illumination system 10 can also have a configurationsimilar to the illumination system disclosed in, for example, Kokai(Japanese Unexamined Patent Publication) No. 6-349701 and itscorresponding U.S. Pat. No. 5,534,970, and the like.

In illumination system 10, an illumination light (exposure light) ILserving as an energy beam illuminates a slit-shaped illumination areaset by the reticle blind on reticle R where the circuit pattern or thelike is fabricated with substantially uniform illuminance. Asillumination light IL, the ArF excimer laser beam (wavelength: 193 nm)is used as an example. As illumination light IL, far ultraviolet lightsuch as the KrF excimer laser beam (wavelength: 248 nm) or bright linesin the ultraviolet region generated by an ultra high-pressure mercurylamp (such as the g-line or the i-line) can also be used. In addition,as the optical integrator, parts such as a fly-eye lens, a rodintegrator (an internal reflection type integrator), or a diffractionoptical element can be used. As long as the national laws in designatedstates or elected states, to which this international application isapplied, permit, the disclosures of the publications, the correspondingU.S. patent, and the corresponding publication of the U.S applicationcited above are fully incorporated herein by reference.

On reticle stage RST, reticle R is fixed, for example, by vacuumsuction. Reticle stage RST is structured finely drivable in an XY planeperpendicular to the optical axis of illumination system 10 (coincidingwith an optical axis AX of the optical system described later) by areticle stage drive section 11 (not shown in FIG. 1, refer to FIG. 6)that includes parts such as a linear motor. Reticle stage RST isstructured also drivable in a predetermined scanning direction (in thiscase, a Y-axis direction, which is the lateral direction of the pagesurface in FIG. 1) at a designated scanning speed.

The position of reticle stage RST within the XY plane is detectedconstantly with a reticle laser interferometer (hereinafter referred toas a ‘reticle interferometer’) 16 via a movable mirror 15, at aresolution, for example, around 0.5 to 1 nm. In actual, on reticle stageRST, a movable mirror that has a reflection surface orthogonal to theY-axis direction and a movable mirror that has a reflection surfaceorthogonal to an X-axis direction are arranged, and corresponding tothese movable mirrors, a reticle Y interferometer and a reticle Xinterferometer are arranged; however in FIG. 1, such details arerepresentatively shown as movable mirror 15 and reticle interferometer16. Incidentally, for example, the edge surface of reticle stage RST maybe polished in order to form a reflection surface (corresponds to thereflection surface of movable mirror 15). In addition, instead of thereflection surface that extends in the X-axis direction used fordetecting the position of reticle stage RST in the scanning direction(the Y-axis direction in this embodiment), at least one corner cubicmirror (such as a retroreflector) may be used. Of the interferometersreticle Y interferometer and reticle X interferometer, one of them, suchas reticle Y interferometer, is a dual-axis interferometer that has twomeasurement axes, and based on the measurement values of reticle Yinterferometer, the rotation of reticle stage RST in a θz direction (therotational direction around a Z-axis) can be measured in addition to theY position of reticle stage RST.

The positional information on reticle stage RST from reticleinterferometer 16 is sent to main controller 20. Main controller 20drives and controls reticle stage RST via reticle stage drive section 11(refer to FIG. 6), based on the positional information of reticle stageRST.

Projection unit PU is disposed below reticle stage RST in FIG. 1.Projection unit PU is equipped with a barrel 40, and an optical system42, which is made up of a plurality of optical elements, or to be morespecific, a plurality of lenses (lens elements) that share the sameoptical axis AX in the Z-axis direction, held at a predeterminedpositional relationship within the barrel. Further, in the embodiment, ahydrostatic pad 32 serving as a fluid static bearing is integrallyattached to the lower end (the tip of barrel 40 that holds the opticalelement (optical member) closest to the image plane side (wafer W side)constituting optical system 42) of barrel 40, and inside an openingformed in the center of hydrostatic pad 32, a solid immersion lens(hereinafter simply referred to as ‘SIL’) 22 is arranged (refer to FIG.3). SIL 22 consists of a plane-convex lens, and its planar surface(hereinafter referred to as a ‘lower surface’ for the sake ofconvenience) faces downward and is arranged so that the lower surface issubstantially co-planar with the bearing surface of hydrostatic pad 32.SIL 22 is made from a material whose refractive index n_(SIL) is around2 to 2.5.

In the embodiment, optical system 42 and SIL 22 inside barrel 40substantially configure a projection optical system consisting of, forexample, a both-side telecentric dioptric system that has apredetermined projection magnification (such as ¼ or ⅕ times).Hereinafter, the projection optical system will be described asprojection optical system PL.

In this case, when the illumination area of reticle R is illuminated byillumination light IL from illumination system 10, illumination light ILthat has passed through reticle R forms a reduced image of the circuitpattern within the illumination area of reticle R (a reduced image of apart of the circuit pattern) on wafer W whose surface is coated with aresist (photosensitive agent), on the irradiation area (hereinafter alsoreferred to as ‘exposure area’) of the illumination light conjugate withthe illumination area, via projection optical system PL.

In addition, although it is omitted in the drawings, among the pluralityof lenses making up optical system 42, a plurality of specific lensesoperate under the control of an image forming quality correctioncontroller 81 (refer to FIG. 6) based on instructions from maincontroller 20, so that optical properties (including image formingquality) of projection optical system PL, such as magnification,distortion, coma, and curvature of image plane (including inclination ofimage plane), and the like can be adjusted.

The configuration and the like of hydrostatic pad 32 and the pipingsystem connecting to hydrostatic pad 32 will be described later in thedescription.

Wafer table TB is constituted by a rectangular plate member, and on itssurface, an auxiliary plate 24 is fixed that has a circular opening(refer to FIG. 2) formed in the center. As is shown in FIG. 2, a gap Dexists between auxiliary plate 24 and wafer W, which is set at 3 mm orunder. In addition, although a notch (a V-shaped cut) is formed in apart of wafer W, it is omitted in the drawings since the notch is around1 mm, smaller than gap D.

In addition, a circular opening is formed in a part of auxiliary plate24, and a fiducial mark plate is embedded tightly into the opening. Thesurface of fiducial mark plate FM is to be co-planar with auxiliaryplate 24. On the surface of fiducial mark plate FM, various kinds offiducial marks (none of which are shown) are formed, which are used forreticle alignment (to be described later), baseline measurement by analignment detection system ALG (also to be described later), and thelike.

In actual fact, as is shown in FIG. 3, an elastic body 25 isincorporated between auxiliary plate 24 and wafer table TB. In thiscase, when hydrostatic pad 32 is not positioned above auxiliary plate24, the upper surface of auxiliary plate 24 is set always lower than theupper surface of wafer W. And, in a state where hydrostatic pad 32 ispositioned above auxiliary plate 24, the upper surface of auxiliaryplate 24 rises until it coincides with the upper surface of wafer W bythe balance of positive pressure and negative pressure of hydrostaticpad 32. This allows the gap between hydrostatic pad 32 and the uppersurface of auxiliary plate 24 facing hydrostatic pad 32 to be constantlymaintained, therefore, the pressure can be maintained at a constantlevel and the amount of water leakage can be substantially reduced tozero.

Wafer table TB is configured movable not only in the scanning direction(the Y-axis direction) but also in the non-scanning direction (theX-axis direction) orthogonal to the scanning direction by the drive unit(to be described later), so that the plurality of shot areas on wafer Wcan be positioned to the exposure area conjugate with the illuminationarea referred to earlier. The arrangement allows wafer table TB toperform a step-and-scan operation in which an operation for scanningexposure of each shot area on wafer W and an operation (movementoperation performed between divided areas) for moving wafer W to theacceleration starting position (scanning starting position) to exposethe next shot are repeated.

In addition, as is shown in FIG. 1, on the lower surface (rear surface)of wafer table TB, a hydrostatic pad 34 serving as a fluid staticbearing is arranged facing hydrostatic pad 32, and hydrostatic pad 34 isfixed on the upper surface of a fixed member 36. In this case, wafertable TB and wafer W placed on wafer table TB are held by hydrostaticpad 32 and hydrostatic pad 34 vertically in a non-contact manner. Theconfiguration and the like of hydrostatic pad 34 and the piping systemconnecting to hydrostatic pad 34 will be described later in thedescription.

In addition, the position of wafer table TB within the XY plane(including rotation around the Z-axis (θz rotation)) is measured with anencoder 96. This point will also be described later in the description.

Next, a drive unit that drives wafer table TB will be described,referring to FIGS. 2 and 3. FIG. 2 shows a perspective view of aconfiguration of a drive unit 50 along with wafer table TB and the like,and FIG. 3 schematically shows the XZ section of drive unit 50, alongwith the piping system for supply/drainage to hydrostatic pads 32 and34.

Drive unit 50 is equipped with a stage 52 (refer to FIG. 2) that movablysupports wafer table TB from below, a first drive mechanism that driveswafer table TB in the Y-axis direction, which is the scanning direction,as well as finely drive wafer table TB in the non-scanning direction(the X-axis direction), and a second drive mechanism that drives wafertable TB integrally with stage 52 in the X-axis direction.

Stage 52 is constituted by a rectangular frame-shaped member (refer toFIG. 3). On the bottom surface of the rectangular frame-shaped member,for example, a pair of X movers 54A and 54B is arranged on both sides inthe Y-axis direction, as is shown in FIG. 2. The movers are eachcomposed of a magnetic pole unit that has a plurality of permanentmagnets arranged at a predetermined spacing in the X-axis direction.And, X stators 56A and 56B, which are each composed of an armature unitand constitute X-axis linear motors 58A and 58B along with X movers 54Aand 54B, respectively, are arranged each extending in the X-axisdirection. X stators 56A and 56B are arranged within the same XY planeat a predetermined spacing in the Y-axis direction, and the X statorsare each supported by support members (not shown). X stators 56A and 56Bhave a U-shaped sectional shape where movers 54A and 54B can be insertedinside, and on at least one surface that faces movers 54A and 54B, the Xstators have a plurality of armature coils arranged at a predeterminedspacing in the X-axis direction.

X-axis linear motors 58A and 58B that have the configuration describedabove drive wafer table TB in the X-axis direction integrally, withstage 52. That is, X-axis linear motors 58A and 58B constitute at leasta part of the second drive mechanism.

As is shown in FIG. 3, wafer table TB is levitationally supported via aclearance of around several μm above the upper surface of stage 52, viaa plurality of air bearings arranged close to the edge of the bottomsurface of wafer table TB on both ends in the X-axis direction.

As is shown in FIG. 2, a pair of Y movers 60A and 60B is arranged,respectively, on the edge surface of wafer table TB on both ends in theX-axis direction at a position substantially in the center of the Y-axisdirection. The movers, for example, are each composed of a magnetic poleunit that has a plurality of permanent magnets arranged at apredetermined spacing in the Y-axis direction. And, Y stators 62A and62B, which constitute Y-axis linear motors 64A and 64B, along with Ymovers 60A and 60B, respectively, are arranged on the upper surface ofstage 52 on both ends of the X-axis direction, each extending in theY-axis direction. Y stators 62A and 62B are each composed of, forexample, an armature unit that has a plurality of armature coilsarranged at a predetermined spacing in the Y-axis direction. Y-axislinear motors 64A and 64B drive wafer table TB in the Y-axis direction.In addition, by slightly differentiating the drive force generated byY-axis linear motors 64A and 64B, wafer table TB can be rotated aroundthe Z-axis.

Furthermore, on the edge surface of wafer table TB on one end (the −Xend) in the X-axis direction, U-shaped permanent magnets 66A and 66B arearranged on the +Y and −Y sides of Y mover 60B. Permanent magnets 66Aand 66B each constitute a voice coil motor, along with Y stator 62B.These voice coil motors finely drive wafer table TB in the X-axisdirection. Hereinafter, these voice coil motors will also be referred toas voice coil motors 66A and 66B using the same reference numerals asthe permanent magnets, which are the movers of the voice coil motors.

As is obvious from the description so far, Y-axis linear motors 64A and64B and voice coil motors 66A and 66B constitute at least a part of thefirst drive mechanism.

Referring back to FIG. 1, alignment detection system ALG by the off-axismethod is arranged on the side surface of barrel 40 of optical unit PU.As alignment detection system ALG, for example, an alignment sensor ofan FIA (Field Image Alignment) system based on an image-processingmethod is used. The alignment sensor irradiates a broadband detectionbeam that does not expose the resist on the wafer on a target mark,picks up the image of the target mark formed on the photodetectionsurface by the reflection light from the target mark and the image of anindex (not shown) using a pick-up device (such as a CCD), and outputsthe imaging signals. And, based on the output of alignment detectionsystem ALG, positional measurement of the fiducial marks on fiducialmark plate FM and alignment marks on wafer W in the X, Y two-dimensionaldirections can be performed.

Next, hydrostatic pads 32 and 34, and the piping connecting to thehydrostatic pads will be described, referring to FIGS. 3 and 4.

As is shown in FIG. 3, on the end (lower end section) of barrel 40 ofoptical unit PU on the image-plane side, a tapered section 40 a isformed whose diameter becomes smaller the lower it becomes. In thiscase, the lens closest to the image plane (not shown) that constitutesoptical system 42, or in other words, the lens second closest to theimage plane that constitutes projection optical system PL, is arrangedinside tapered section 40 a.

As an example of hydrostatic pad 32 attached below barrel 40, a thickpad that has a annular shape (donut shape) whose outer diameter isapproximately 60 mm, inner diameter is approximately 35 mm, and theheight around 20 to 50 mm is used. Hydrostatic pad 32 is fixed in astate where its bearing surface (the bottom surface) is parallel to theXY plane, with the surface (the upper surface) opposite to the bearingsurface fixed to the lower end surface of barrel 40. Accordingly, in theembodiment, the positional relation between hydrostatic pad 32 andprojection optical system PL relative to the direction of optical axisAX of projection optical system PL is maintained constant.

On the bearing surface (the bottom surface) of hydrostatic pad 32, as itcan be seen when viewing FIG. 3 together with FIG. 4, which is a view ofthe bottom surface of hydrostatic pad 32, a ring-shaped drainage groove68 serving as a liquid drainage groove (a groove), a ring-shaped watersupply groove 70 serving as a liquid supply groove (a groove), and aring-shaped drainage groove 72 serving as a liquid drainage groove (agroove) are sequentially formed from the inside to the outsideconcentrically. In FIG. 3, of the three grooves 68, 70, and 72, thegroove width of water supply groove 70 in the middle is around twice thewidth of the remaining two grooves. However, the area ratio of groove 70and groove 72 is to be decided so that each of the positive pressureforce and negative pressure force are well balanced.

On the inner bottom surface (the inner upper surface in FIG. 3) ofdrainage groove 72, a plurality of through holes 74 that penetrate thebottom surface in the vertical direction are formed at a substantiallyequal spacing. And, one end of drainage pipes 76 connects to each of thethrough holes 74.

Similarly, on the inner bottom surface (the inner upper surface in FIG.3) of water supply groove 70, a plurality of through holes 78 thatpenetrate the bottom surface in the vertical direction are formed at asubstantially equal spacing. And, one end of water supply pipes 80connects to each of the through holes 78.

Similarly, on the inner bottom surface (the inner upper surface in FIG.3) of drainage groove 68, a plurality of through holes 82 that penetratethe bottom surface in the vertical direction are formed at asubstantially equal spacing. And, one end of drainage pipes 84 connectsto each of the through holes 82.

The other end of each of the water supply pipes 80 each connect viavalves 86 a to the other end of a supply line 90, which has one endconnecting to a liquid supply unit 88. Liquid supply unit 88 is composedincluding a liquid tank, a compression pump, a temperature control unit,and the like, and operates under the control of main controller 20. Inthis case, when liquid supply unit 88 operates when the correspondingvalve 86 a is open, for example, a predetermined liquid used forimmersion whose temperature is controlled so that it is about the sametemperature as that in a chamber (drawing omitted) where (the main bodyof) exposure apparatus 100 is housed is supplied into water supplygroove 70 of hydrostatic pad 32, via supply line 90, water supply pipe80, and through hole 78 in sequence. Hereinafter, valves 86 a arrangedin each of the water supply pipes 80 will also be considered togetherand referred to as valve group 86 a (refer to FIG. 6).

As the liquid referred to above, in this case, ultra pure water(hereinafter, it will simply be referred to as ‘water’ besides the casewhen specifying is necessary) that transmits the ArF excimer laser beam(light with a wavelength of 193.3 nm) is to be used. Ultra pure watercan be obtained in large quantities at a semiconductor manufacturingplant or the like, and it also has an advantage of having no adverseeffect on the photoresist on the wafer or to the optical lenses. Inaddition, ultra pure water has no adverse effect on the environment andit also has an extremely low concentration of impurities, therefore,cleaning action on the surface of the wafer and the surface of SIL 22can be anticipated.

The other end of each of the drainage pipes 76 each connect via valves86 b to the other end of a drainage line 94, which has one endconnecting to a liquid recovery unit 92. Liquid recovery unit 92 iscomposed including a liquid tank, a vacuum pump (or a suction pump), andthe like, and operates under the control of main controller 20. In thiscase, when the corresponding valve 86 b is open, liquid recovery unit 92recovers the water existing between the bearing surface of hydrostaticpad 32 and the surface of wafer W near drainage groove 72, via drainagepipes 76. Hereinafter, valves 86 b arranged in each of the drainagepipes 76 will also be considered together and referred to as valve group86 b (refer to FIG. 6).

The other end of each of the drainage pipes 84 is drawn inside a tank(not shown). The inside of the tank is open to the atmosphere.

Similar to hydrostatic pad 32, a thick pad that has an annular shape(donut shape) whose outer diameter is approximately 60 mm, innerdiameter is approximately 35 mm, and the height around 20 to 50 mm isused as hydrostatic pad 34. Hydrostatic pad 34 is fixed to the uppersurface of fixed member 36 so that the bearing surface (upper surface)of hydrostatic pad 34 is parallel to the XY plane.

On the rear surface of wafer table TB, an XY two-dimensional scale (notshown) is formed, and encoder 96 that can optically (or magnetically)read the XY two-dimensional scale is disposed inside the opening formedin the center of hydrostatic pad 34. Accordingly, when a part of wafertable TB faces encoder 96, encoder 96 can measure the positionalinformation of wafer table TB within the XY plane at a predeterminedresolution, such as, for example, 0.2 nm. The measurement values ofencoder 96 are supplied to main controller 20 (refer to FIG. 6). Becausewafer table TB is rigidly pressed by the vertical hydrostatic pads 32and 34, there is no flexure in the section of wafer table TB clamped byhydrostatic pads 32 and 34, which makes sign errors due to flexure ofwafer table TB included in the measurement values of encoder 96extremely small.

On the bearing surface of hydrostatic pad 34, in exactly the samearrangement and shape, a water supply groove 102 is formed serving as aliquid supply groove (a groove), as well as drainage grooves 104 and 106serving as liquid drainage grooves (grooves) on the outside and insideof water supply groove 102. Similar to the earlier description, grooves102, 104, and 106 have a plurality of through holes that penetrate thebottom surface of hydrostatic pad 34. And, one end of a plurality ofwater supply pipes 108 connects to water supply groove 102 via theplurality of through holes, respectively, while the other end of each ofthe water supply pipes 108 connect to a liquid supply unit 114 (notshown in FIG. 3, refer to FIG. 6) via valves 86 c and water supply lines(not shown). The configuration of liquid supply unit 114 is the same asliquid supply unit 88 previously described.

One end of each of a plurality of drainage pipes 110 connects todrainage groove 104 on the outer side, via each of the plurality ofthrough holes, whereas the other end of each of the plurality ofdrainage pipes 110 connects to a liquid recovery unit 116 (not shown inFIG. 3, refer to FIG. 6) via valves 86 d and a recovery line (notshown). The configuration of liquid recovery unit 116 is the same asliquid recovery unit 92 previously described.

Similar to the description above, one end of each of a plurality ofdrainage pipes 112 connects to drainage groove 106 on the inner side,via each of the plurality of through holes, whereas the other end ofeach of the plurality of drainage pipes 112 connects to liquid recoveryunit 116 via valves 86 e and the recovery line (not shown). That is, inhydrostatic pad 34, drainage groove 106 on the inner side is not open tothe atmosphere.

In the description below, valves 86 c arranged on the other end of eachof the plurality of water supply pipes 108 will also be consideredtogether and referred to as valve group 86 c (refer to FIG. 6).Similarly, valves 86 d and 86 e arranged on the other end of each of theplurality of drainage pipes 110 and 112 will also be considered togetherand referred to as valve groups 86 d and 86 e (refer to FIG. 6).

As each of the valves referred to above, adjustment valves (such as aflow control valve) or the like that open and close, and whose openingdegree can also be adjusted are used. These valves operate under thecontrol of main controller 20 (refer to FIG. 6).

FIG. 6 is a block diagram of a configuration of a control system ofexposure apparatus 100, with the configuration partially omitted. Thecontrol system is mainly composed of main controller 20, which is madeup of a workstation (or a microcomputer) or the like.

Next, the support of wafer table TB by hydrostatic pads 32 and 34 inexposure apparatus 100 of the embodiment will be described with theoperation of main controller 20, referring to FIGS. 3, 5, and 6, and thelike.

First of all, the situation will be described where the support of wafertable TB begins, for example, by hydrostatic pads 32 and 34, which arein a static state.

Main controller 20 firstly begins to supply water from liquid supplyunit 88 to hydrostatic pad 32 on the upper side in a state where valvegroup 86 a is opened to a predetermined degree, and also begins theoperation of liquid recovery unit 92 in a state where valve group 86 bis opened to a predetermined degree. This operation sends water of apredetermined pressure (positive pressure) into water supply groove 70of hydrostatic pad 32, via supply line 90 and each of the water supplypipes 80 from liquid supply unit 88. Apart of the water sent into watersupply groove 70 that passes through the inside of water supply groove70 between the bearing surface of hydrostatic pad 32 and wafer W isrecovered by liquid recovery unit 92, via drainage groove 72, each ofthe through holes 74, drainage pipes 76, and drainage line 94 (refer toFIG. 5).

In addition, at substantially the same timing as when the water supplyto hydrostatic pad 32 described above begins, main controller 20 beginsto supply the water from liquid supply unit 144 to hydrostatic pad 34 onthe lower side in a state where valve group 86 c is opened to apredetermined degree, while beginning to operate liquid recovery unit116 in a state where valve groups 86 d and 86 e are respectively openedto a predetermined degree. This operation sends water of a predeterminedpressure (positive pressure) into water supply groove 102 of hydrostaticpad 34, via a supply line and each of the water supply pipes 108 fromliquid supply unit 114. After the water supplied fills in the inside ofwater supply groove 102 of hydrostatic pad 34 and the space between thebearing surface of hydrostatic pad 34 and wafer table TB, the water isrecovered by liquid recovery unit 116, via drainage grooves 104 and 106,each of the through holes, and drainage pipes 110 and 112 (refer to FIG.5). During this operation, main controller 20 sets the degree of openingof each valve in valve groups 86 d and 86 e, the pressure of watersupplied from liquid supply unit 114, the negative pressure that liquidrecovery unit 116 generates within drainage pipes 110 and 112, and thelike, so that the amount of water supplied to hydrostatic pad 34substantially coincides with the amount of water drained fromhydrostatic pad 34 via drainage grooves 104 and 106. As a result, acertain amount of water is constantly filled in the space betweenhydrostatic pad 34 and wafer table TB. Accordingly, the thickness of thelayer of water between the bearing surface of hydrostatic pad 34 andwafer table TB is constant at all times, and wafer table TB is supportedby hydrostatic pad 34 with high rigidity. In this case, the pressure ofthe water between hydrostatic pad 34 and wafer table TB acts as apreload (pressurization force) to hydrostatic pad 32 on the upper side.That is, wafer table TB is always pressed from below at a constantforce.

In this case, main controller 20 sets the degree of opening of eachvalve in valve groups 86 a and 86 b, the pressure of the water suppliedfrom liquid supply unit 88, the negative pressure that liquid recoveryunit 92 generates within each of the drainage pipes 76, and the like, sothat the amount of water supplied to hydrostatic pad 32 is slightlylarger than the amount of water drained from drainage groove 72.Therefore, the remaining water that is supplied to hydrostatic pad 32but is not drained from drainage groove 72 is drained outside via eachof the through holes 82 and drainage pipes 84 formed in drainage groove68, after the water fills in the space (including the space below SIL22) between the bearing surface of hydrostatic pad 32 and wafer tableTB.

Because drainage groove 68 is a passive drainage groove open to theatmosphere, the water existing in the space between SIL 22 and wafer Wis in a state open to the atmosphere. Accordingly, there is almost nohydrostatic on SIL 22, which makes a stress free state.

Meanwhile, the water near the inside of water supply groove 70 is underhigh pressure (positive pressure), which gives a high load capacity andrigidity to hydrostatic pad 32. In addition, the space betweenhydrostatic pad 32 and the surface of wafer W is constantly filled witha certain amount of water, and liquid recovery unit 93 constantlyrecovers a part of the water filled by a certain amount. As a result,the gap (the so-called bearing gap) between the bearing surface ofhydrostatic pad 32 and the surface of wafer W is constantly maintained.

Accordingly, in the embodiment, the area of wafer table TB and wafer Wmounted on wafer table TB in the vicinity of SIL 22 is supported withhigh rigidity, in a state vertically clamped by hydrostatic pads 32 and34.

And, when wafer table TB moves in a predetermined direction, like thedirection in FIG. 5 indicated by arrow C, a water flow indicated byarrow F in FIG. 5 is generated below SIL 22. The water flow indicated byarrow F is a laminar Couette flow that is generated when shear force dueto relative displacement of the surface of wafer W and the lower surfaceof SIL 22 is applied to the water, which is an incompressible viscousfluid as well as a Newtonian fluid that obeys Newton's law of viscosity.

In exposure apparatus 100 of the embodiment, when wafer table TB andwafer W are driven while being clamped by hydrostatic pads 32 and 34 inthe manner described above as in, for example, the stepping operation inbetween shots of wafer table TB (to be described later) and the scanningexposure operation, a viscous Couette flow corresponding to the drivedirection occurs, which makes the water under SIL 22 replace.

In exposure apparatus 100 of the embodiment that has the configurationdescribed above, in the same manner as in a typical scanning stepper,predetermined preparatory operations are performed such as reticlealignment that uses a reticle alignment system (not shown), alignmentdetection system ALG, and fiducial mark plate FM earlier described, andwafer alignment as in baseline measurement of alignment detection systemALG, and wafer alignment by EGA (Enhanced Global Alignment), and thelike. Details on preparatory operations such as reticle alignment,baseline measurement, and the like described above are disclosed in, forexample, Kokai (Japanese Unexamined Patent Publication) No. 7-176468 andthe corresponding U.S. Pat. No. 5,646,413, and details on the followingoperation, EGA, are disclosed in, for example, Kokai (JapaneseUnexamined Patent Publication) No. 61-44429 and the corresponding U.S.Pat. No. 4,780,617. As long as the national laws in designated states(or elected states), to which this international application is applied,permit, the above disclosures of each of the publications and thecorresponding U.S. patents are incorporated herein by reference.

Then, when wafer alignment is completed, main controller 20 begins thewater supply operation described earlier to hydrostatic pads 32 and 34,and then as is described earlier, wafer table TB and wafer W mounted onwafer table TB are clamped by hydrostatic pads 32 and 34 with highrigidity.

Next, based on the wafer alignment results, main controller 20 moveswafer table TB to the acceleration starting position for exposing thefirst shot area (first shot) serving as a first divided area on wafer W,via drive unit 50.

When wafer W has been moved to the acceleration starting positiondescribed above, main controller 20 begins relative scanning of reticlestage RST and wafer table TB in the Y-axis direction, via reticle stagedrive section 11 and the first drive mechanism (Y-axis linear motors 64Aand 64B, and voice coil motors 66A and 66B) of drive unit 50. Then, whenreticle stage RST and wafer table TB each reach their target scanningspeed and move into a constant speed synchronous state, illuminationlight (ultraviolet pulse light) IL from illumination system 10 begins toilluminate the pattern area of reticle R, and scanning exposure begins.The relative scanning described above is performed by main controller20, which controls reticle stage drive section 11 and the first drivemechanism while monitoring the measurement values of encoder 96 andreticle interferometer 16 previously described.

Especially during the scanning exposure described above, main controller20 synchronously controls reticle stage RST and wafer table TB so thatmovement speed Vr of reticle stage RST in the Y-axis direction andmovement speed Vw of wafer table TB in the Y-axis direction aremaintained at a speed ratio corresponding to the projectionmagnification of projection optical system PL.

Then, different areas in the pattern area of reticle R are sequentiallyilluminated by illumination light IL, and when the entire pattern areahas been illuminated, scanning exposure of the first shot is completed.By this operation, the pattern of reticle R is reduced and transferredonto the first shot via projection optical system PL.

When scanning exposure of the first shot on wafer W is completed in thismanner, main controller 20 steps wafer table TB via the second drivemechanism (X-axis linear motors 58A and 58B) of drive unit 50, forexample, in the X-axis direction, to the acceleration starting positionfor exposing the second shot (the shot area serving as a second dividedarea) on wafer W. Next, scanning exposure of the second shot on wafer Wis performed in the manner similar to the description above, under thecontrol of main controller 20.

In this manner, scanning exposure of the shot area on wafer W and thestepping operation between shot areas are repeatedly performed, and thecircuit pattern of reticle R is sequentially transferred onto the shotareas of wafer W serving as a plurality of divided areas.

On the stepping operation between shot areas of wafer table TB and onthe scanning exposure operation described above, because the viscousCouette flow described above is generated in the direction correspondingto the drive direction of wafer table TB, the water below SIL 22 isconstantly replaced. Accordingly, in exposure apparatus 100, immersionexposure is performed constantly using water fresh and stable intemperature.

In addition, for example, in the case the periphery shot areas on waferW are exposed, the case may occur when at least a part of the bearingsurface of hydrostatic pad 32 moves away from wafer W, however on wafertable TB, since auxiliary plate 24 previously described is arranged inthe periphery of wafer W, the state where the entire bearing surface ofhydrostatic pad 32 faces either wafer W or the auxiliary plate can bemaintained. In this case, when hydrostatic pad 32 is positioned aboveauxiliary plate 24 as is earlier described, the upper surface ofauxiliary plate 32 rises to coincide with the upper surface of wafer Wdue to the balance of positive pressure and negative pressure ofhydrostatic pad 32. Accordingly, the water supplied to hydrostatic pad32 can be held by hydrostatic pad 32 and by auxiliary plate 24 or waferW, and leakage of the water can be prevented.

As is obvious from the description so far, in the embodiment,hydrostatic pad 32, liquid supply unit 88, liquid recovery unit, 92, andthe water supply/drainage system (to be more specific, drainage pipes76, water supply pipes 80, drainage pipes 84, valve groups 86 a and 86b, supply line 90, and drainage line 94) connecting to the parts aboveconstitute a liquid bearing unit.

As is described in detail above, according to exposure apparatus 100 ofthe embodiment, the hydrostatic bearing unit described above maintainsthe distance between the bearing surface of hydrostatic pad 32 and thesurface of wafer W mounted on wafer table TB in the direction of opticalaxis AX (the Z-axis direction) of projection optical system PL at apredetermined amount (e.g., around 10 μm). Further, on the rear surfaceside of wafer table TB, hydrostatic pad 34 serving as a fluid staticbearing is arranged facing hydrostatic pad 32. And, by hydrostatic pad34, the water is supplied to the space between the bearing surface thatfaces the rear surface of wafer table TB and the wafer table, and by thestatic pressure of the water, the gap between the bearing surface andthe wafer table is maintained. As a result, wafer table TB and wafer Wmounted on wafer table TB are clamped with hydrostatic pads 32 and 34,vertically. In this case, the distance between each of the bearingsurfaces of hydrostatic pads 32 and 34 and wafer W or wafer table TB canbe maintained stably and constantly at, for example, around 10 μm orunder. Different from static gas bearings, since hydrostatic bearingssuch as the hydrostatic pads utilize the static pressure of the water(liquid), which is an incompressible fluid, between the bearing surfaceand the support object (wafer W or wafer table TB), the rigidity of thebearings is high and the distance between the bearing surface and thesupport object can be maintained stably and constantly. In addition,when compared to gas (e.g., air), water (liquid) is higher in viscosityand liquid is superior in vibration damping than gas. As a result, theposition of wafer table TB and wafer W in the Z-axis direction (thedirection of optical axis AX) does not shift in at least the exposurearea and the neighboring area, while wafer table TB and wafer W arebeing moved.

Therefore, according to exposure apparatus 100 of the embodiment, thepattern of reticle R can be transferred onto the plurality of shot areason wafer W in a state where defocus caused by the movement of wafertable TB is substantially prevented for certain, without necessarilyhaving to arrange a focal position detection system such as a focussensor.

In addition, in exposure apparatus 100 of the embodiment, because wafertable TB and wafer W are clamped with high rigidity by hydrostatic pads32 and 34 in the strip-shaped area (the area corresponding to thebearing surfaces of hydrostatic pads 32 and 34) around SIL 22 thatincludes the projection area (exposure area) of the pattern on wafer W,the rigidity of wafer table TB itself does not have to be so high. As aresult, the thickness of wafer table TB can be reduced, which reducesthe weight of wafer table TB and allows the position controllability tobe improved. For example, the thickness of wafer table TB can be reducedto around a quarter or under the conventional tables. That is, thethickness of wafer table TB can be set to around 10 mm or under.

In addition, in exposure apparatus 100 of the embodiment, wafer W isexposed by illumination light IL in a state where water (high refractiveindex fluid) that has a higher refractive index than air constantlyexists in the space between the lower surface of SIL 22 being theoptical member of projection optical system PL closest to the imageplane and the surface of wafer W, via the pattern area of reticle R,projection optical system PL, and the water. That is, immersion exposureis performed, which shortens the wavelength of illumination light IL onthe surface of wafer W to 1/n^(th) of the wavelength in the air (n isthe refractive index of liquid, in the case of water, n is 1.4), whichin turn widens the effective depth of focus n times compared to thedepth of focus in the air. Accordingly, exposure can be performed withhigh resolution. In the case the depth of focus that has to be securedis about the same as when exposure is performed in the air, thenumerical aperture (NA) of projection optical system PL can beincreased, which can also improve the resolution.

In addition, when the effective depth of focus widens n times comparedto the depth of focus in the air, it also has the effect of being ableto suppress defocus.

In addition, in exposure apparatus 100 of the embodiment, because thewater supplied to hydrostatic pad 32 is constantly replaced as ispreviously described during scanning exposure or the like, the waterflow removes foreign objects that adhere to wafer W.

In addition, according to exposure apparatus 100 of the embodiment, evenwhen wafer table TB moves to a position where projection optical systemPL is away from wafer W in a state where the water is held in the spacebetween projection optical system PL and wafer W, such as when exposingshot areas in the periphery of wafer W or when exchanging the substrateon wafer table TB after exposure has been completed, the water can beheld in the space between projection optical system PL and auxiliaryplate 24 and water leakage can be prevented. Accordingly, variousinconveniences that occur due to water leakage can be prevented.Further, because the gap between auxiliary plate 24 and wafer W is setto 3 mm or under, the liquid is kept from flowing out into the gapbetween wafer W and auxiliary plate 24 due to the surface tension of theliquid, while wafer table TB moves from the state where wafer W is belowprojection optical system PL to a position where wafer W is away fromprojection optical system PL.

Therefore, according to exposure apparatus 100 of the present invention,due to the various effects described above, the pattern of reticle R canbe transferred onto each of the plurality of shot areas on wafer W withextremely good precision. In addition, exposure can be performed with awider depth of focus than the depth of focus in the air.

In addition, in exposure apparatus 100 of the embodiment, because thelower surface of SIL 22 being the optical member of projection opticalsystem PL closest to the image plane substantially coincides with thebearing surface of hydrostatic pad 32, the distance between SIL 22 andthe surface of wafer W is around 10 μm, which is the distance betweenhydrostatic pad 32 and wafer W. Accordingly, the amount of liquidsupplied for immersion exposure can be reduced and the water can also berecovered smoothly after the immersion exposure, which allows wafer W todry easily after the water recovery.

In addition, because the thickness of the layer of water is extremelythin, absorption of illumination light IL by the water is small.Furthermore, optical aberration caused by the uneven water temperaturecan be suppressed.

In the embodiment above, the case has been described where wafer tableTB and wafer W are clamped vertically with high rigidity by hydrostaticpads 32 and 34. However, since the purpose of hydrostatic pad 34 inparticular, which is arranged below wafer table TB, is mainly to providea constant preload (pressurization) to hydrostatic pad 32 on the upperside, hydrostatic pad 34 does not necessarily have to be arranged aslong as a constant upward force can be provided to the rear surface ofwafer table TB. Or, instead of hydrostatic pad 34, other types of fluidbearings can also be used, such as for example, vacuum preload airbearings or the like that has high bearing rigidity among static gasbearings that utilize static pressure of pressurized gas.

In addition, in the embodiment above, the case has been described wherea part of the water supplied to hydrostatic pad 32 is used for immersionexposure. The present invention, however, is not limited to this, andthe liquid for immersion exposure may also be supplied to the spacebetween projection optical system PL and wafer W via a supply pathcompletely independent from the supply path that supplies the water tohydrostatic pad 32.

Furthermore, in the embodiment above, the case has been described wherethe present invention is applied to an exposure apparatus that performsimmersion exposure. However, the method of supporting a moving body suchas wafer table TB using hydrostatic bearings as in hydrostatic pads canalso be suitably applied to an exposure apparatus that does not performimmersion exposure. Even in such a case, hydrostatic bearings maintainthe distance between the bearing surface and the surface of thesubstrate (wafer) in the optical axis direction at a predeterminedamount (e.g., around 10 μm). Different from static gas bearings, sincehydrostatic bearings utilize static pressure of the liquid, which is anincompressible fluid, between the bearing surface and the support object(substrate), the rigidity of the bearings is high, which allows thedistance between the bearing surface and the substrate to be stably andconstantly maintained. Further, liquid (such as pure water) is higher inviscosity than gas (such as air), and is also superior in vibrationdamping than gas. Therefore, according to the exposure apparatus of thepresent invention, pattern transfer onto a substrate almost free fromdefocus can be achieved, without necessarily having to arrange a focalposition detection system.

In the embodiment above, the case has been described where donut-shapedhydrostatic pad 32 is arranged on the upper side (the image plane sideof projection optical system PL) of wafer W on wafer table TB andhydrostatic pad 34 is arranged on the lower side of wafer table TB. Thepresent invention, however, is not limited to this, and a hydrostaticbearing that has a rectangular annular bearing surface surrounding theexposure area (the projection area of the reticle pattern) may bearranged, instead of at least one of hydrostatic pad 32 and/orhydrostatic 34 described above.

In addition, instead of hydrostatic pad 32, a plurality of smallhydrostatic pads can be attached near the lower end of projectionoptical system PL, surrounding the exposure area (the projection area ofthe reticle pattern). Similarly, instead of hydrostatic pad 34, aplurality of small fluid static bearings may be arranged facing the rearsurface of wafer table TB, in area that corresponds to the areasurrounding the exposure area (the projection area of the reticlepattern). Or, one, two or more hydrostatic pads arranged instead ofhydrostatic pad 32 may be arranged on the side of the image plane ofprojection optical system PL, while the positional relation betweenprojection optical system PL is maintained.

In the embodiment above a focal position detection system (focus sensor)is not provided in particular. In the case a focus sensor is necessary,however, a gap sensor, which measures the spacing between hydrostaticpad 32 and the surface of wafer W at one or more measurement point maybe arranged on hydrostatic pad 32, and based on the measurement valuesof the gap sensor, the liquid recovery unit (or main controller 20) canadjust the negative pressure generated inside drainage pipes 76connecting to hydrostatic pad 32 so as to adjust the position (focus) ofthe surface of wafer W in the Z-axis direction. In this case, as the gapsensor, a pressure sensor can be used that measures the differencebetween the hydrostatic acting on a diaphragm arranged on a part ofhydrostatic pad 32 and the atmospheric pressure, and converts thedifference into distance. Or, a capacitive sensor can also be used.Further, for example, a detection beam can be irradiated on wafer W viaan optical element, which is at least a part of projection opticalsystem PL, for measuring the spacing between projection optical systemPL and wafer W by receiving the reflection beam, and the spacing betweenhydrostatic pad 32 and the surface of wafer W can be adjusted accordingto the measurement values.

In the embodiment above, the case has been described where an optical(or a magnetic) encoder 96 reads the XY two-dimensional scale formed onthe rear surface of wafer table TB in order to measure the position ofwafer table TB within the XY plane. The present invention, however, isnot limited to this, and a laser interferometer may be used to measurethe positional information of wafer table TB within the XY plane.

In this case, the edge surface (e.g., the edge surface on the +X side)of wafer table TB on one end of the X-axis direction and the edgesurface (e.g., the edge surface on the −Y side) of wafer table TB on oneend of the Y-axis direction have to be mirror polished. However, as itcan be seen in FIG. 2, Y mover 60A of Y-axis linear motor 64A isarranged on the edge surface on the +X side, therefore, in such a state,the edge surface on the +X side might not be able to be mirror polishedentirely in the Y-axis direction. In this case, by shifting the positionof both Y movers 60A and 60B in the Z-axis direction as is shown in FIG.7, the edge surface of wafer table TB on the +X side can be mirrorpolished entirely in the Y-axis direction. By arranging Y movers 60A and60B at a point symmetry position with respect to center of gravity G ofwafer table TB, the thrust of Y-axis linear motors 64A and 64B can bemade to act on center of gravity G of wafer table TB.

On the reflection surface made in the manner described above,measurement beams from an interferometer 18 (FIG. 7 shows theinterferometer used only for measurement in the X-axis direction) isirradiated, and when interferometer 18 receives the reflection beams,interferometer 18 measures the position of wafer table TB in the X-axisdirection and the Y-axis direction at a resolution, for example, around0.5 to 1 nm. In this case, as the interferometer, a multi-axisinterferometer that has a plurality of measurement axes can be used, andwith this interferometer, other than the X, Y positions of wafer tableTB, rotation (yawing (θz rotation, which is rotation around the Z-axis),rolling (θy rotation, which is rotation around the Y-axis, and pitching(θx rotation, which is rotation around the X-axis)) can also bemeasured.

Modified Example

In the description so far, the case has been described where hydrostaticpad 32 is fixed to barrel 40 and the position relation betweenprojection optical system PL and hydrostatic pad 32 is constantlymaintained. The present invention, however, is not limited to this, andfor example, as the optical element that constitutes projection opticalsystem PL closest to the image plane, a divided lens, which isvertically divided into two, as is shown in FIG. 8, may be used. Dividedlens 150 in FIG. 8 is composed of a first segment lens 152 a of ahemispheric shape arranged on the lower side, and a second segment lens152 b. Second segment lens 152 b has an inside (inner surface), which isa spherical surface whose radius of curvature has the same center pointas the outer surface (a part of the spherical surface) of the firstsegment lens 152 a but is slightly larger than the radius of curvatureof the first segment lens 152 a, and an outside (outer surface), whichis a spherical surface whose center is a point different from the centerof the first segment lens 152 a. In this case, the first segment lens152 a is a plane-convex lens and the second segment lens 152 b is aconcave meniscus lens.

Divided lens 150 configured in the manner described above can be usedinstead of SIL 22 in the embodiment above. In this case, the secondsegment lens 152 b is integrally attached to barrel 40, and the firstsegment lens 152 a is to be held by hydrostatic pad 32 so that thebearing surface of hydrostatic pad 32 and the lower surface of the firstsegment lens 152 a becomes substantially co-planar with each other.Then, the liquid (such as water) for immersion is to be filled in thespace not only under the first segment lens 152 a (the space between thefirst segment lens 152 a and wafer W), but also in the gap between thefirst segment lens 152 a and the second segment lens 152 b. When such aconfiguration is employed, in the case the first segment lens 152 a ispressurized too much by the hydrostatic acting on the first segment lens152 a, the first segment lens 152 a moves vertically with hydrostaticpad 32, which can suppress unnecessary stress being generated in thefirst segment lens 152 a, which in turn can prevent the opticalperformance from deteriorating. In this case, the vertical movement ofthe first segment lens 152 a and hydrostatic pad 32 sets the pressure(positive pressure) within the water supply groove and the pressure(negative pressure) within the drainage groove at an even balance, whichmakes the thickness of the water layer (water film) under the firstsegment lens 152 a constant, and by the vertical movement of the firstsegment lens 152 a, the optical path changes, which makes it possible toautomatically adjust the focus position.

In the embodiment, divided lens 150 is divided into a plane-convex lensand a concave meniscus lens. However, the optical element on the upperside close to the pupil plane of projection optical system PL can be aplane-convex lens and the optical element on the lower side close to theimage plane of projection optical system PL can be a non-refractivepower parallel plane plate. In this case, when the image formingcharacteristics such as the image plane of the projection optical systemPL change by the shift of the parallel plane plate, at least one ofmoving a part of the lens of the projection optical system, moving thereticle, or finely adjusting the wavelength of the exposure light can beperformed, in order to compensate for the changes in the image formingcharacteristics.

In the first embodiment above, the case has been described where thepresent invention has been applied to an exposure apparatus equippedwith one wafer table TB and one stage 52 that supports the wafer table.The present invention, however, is not limited to this, and the presentinvention may also be suitably applied to an exposure apparatus that hasa plurality (e.g., two) of wafer tables TB and stages, as in thefollowing second embodiment.

Second Embodiment

Next, an exposure apparatus of a second embodiment of the presentinvention is described, referring to FIGS. 9 and 10. FIG. 9 is a planarview showing a configuration of a wafer stage unit 300 that constitutesthe exposure apparatus of the second embodiment. From the viewpoint ofpreventing redundant explanations, the same reference numerals will beused for parts that have the same or similar arrangement as the firstembodiment previously described, and the description thereabout will beomitted.

In the exposure apparatus of the second embodiment, optical unit PU, andan alignment detection system ALG′ similar to alignment detection systemALG is disposed in the Y-axis direction spaced apart at a predetermineddistance. And, below optical unit PU, drive unit 50 described earlier isdisposed, and wafer W is to be mounted on a wafer table TB1 provided onstage 52, which constitutes drive unit 50. In addition, below analignment detection system ALG′, an XY stage unit 180 is disposed. Awafer table TB2 is provided on a stage 171 that constitutes XY stageunit 180, and wafer W is to be mounted on wafer table TB2.

XY stage unit 180 is equipped with stage 171 constituted by arectangular member, which has the same shape as the outer shape of stage52 previously described, an X-axis linear motor 178 that drives stage171 in the X-axis direction, and a pair of Y-axis linear motors 176A and176B that drive stage 171 in the Y-axis direction integrally with X-axislinear motor 178.

Y-axis linear motors 176A and 176B are constituted by Y stators (Y-axislinear guides) 172A and 172B that are arranged in the X-axis directionnear both ends of X stator 56A, which constitutes drive unit 50,respectively extending in the Y-axis direction, and Y movers (sliders)174A and 174B that separately engage with Y stators 172A and 172B,respectively. That is, with one of the Y stators, 172A, and one of the Ymovers, 174A, Y linear motor 176A is configured that generates a driveforce that drives Y mover 174A in the Y-axis direction by theelectromagnetic interaction of Y stator 172A and Y mover 174A, whereas,with the other Y stator, 172B, and the other Y mover, 174B, Y linearmotor 176B is configured that generates a drive force that drives Ymover 174B in the Y-axis direction by the electromagnetic interaction ofY stator 172B and Y mover 174B.

Y movers 174A and 174B are respectively fixed to both ends of the Xstator (X-axis linear guide) extending in the X-axis direction thatconstitutes X linear motor 178 described above. And, on stage 171, an Xmover is arranged corresponding to the X stator of X linear motor 178,and by X linear motor 178 constituted by the X mover and the X stator178, stage 171 is driven in the X-axis direction.

In this case, stage 171 is driven in the X-axis direction by X linearmotor 178, and stage 171 is also driven in the Y-axis directionintegrally with X linear motor 178 by the pair of Y linear motors 176Aand 176B.

On the upper surface of stage 171 on both ends in the X-axis direction,Y stators 162A and 162B are arranged, respectively, extending in theY-axis direction.

Wafer tables TB1 and TB2 both have exactly the same configuration aswafer table TB previously described, and similarly, wafer tables TB1 andTB2 each have Y mover 60A arranged on one end in the X-axis direction,and permanent magnets 66A and 66B and Y mover 60B arranged on the otherend in the X-axis direction.

According to wafer stage unit 300 in FIG. 9, Y mover 60A arranged inwafer table TB1 not only generates a drive force in the Y-axis directionby electromagnetic interaction with Y stator 62A in a state (the statein FIG. 9) where Y mover 60A is engaged with Y stator 62A on stage 52,but also in a state where Y mover 60A is engaged with Y stator 162A onstage 171, Y mover 60A generates a drive force in the Y-axis directionby electromagnetic interaction with Y stator 162A.

Similarly, Y mover 60A arranged in wafer table TB2 not only generates adrive force in the Y-axis direction by electromagnetic interaction withY stator 162A in a state (the state in FIG. 9) where Y mover 60A isengaged with Y stator 162A on stage 171, but also in a state where Ymover 60A is engaged with Y stator 62A on stage 52, Y mover 60Agenerates a drive force in the Y-axis direction by electromagneticinteraction with Y stator 62A.

Similarly, Y mover 60B arranged in wafer table TB1 not only generates adrive force in the Y-axis direction by electromagnetic interaction withY stator 62B in a state (the state in FIG. 9) where Y mover 60B isengaged with Y stator 62B onstage 52, but also in a state where Y mover60B is engaged with Y stator 162B on stage 171, Y mover 60B generates adrive force in the Y-axis direction by electromagnetic interaction withY stator 162B.

Similarly, Y mover 60B arranged in wafer table TB2 not only generates adrive force in the Y-axis direction by electromagnetic interaction withY stator 162B in a state (the state in FIG. 9) where Y mover 60B isengaged with Y stator 162B on stage 171, but also in a state where Ymover 60B is engaged with Y stator 62B on stage 52, Y mover 60Bgenerates a drive force in the Y-axis direction by electromagneticinteraction with Y stator 62B.

In addition, permanent magnets 66A and 66B arranged in wafer table TB1each constitute a voice coil motor that finely moves wafer table TB1 onstage 52 in the X-axis direction in a state (the state in FIG. 9) wherepermanent magnets 66A and 66B are each engaged with Y stator 62B, aswell as constitute a voice coil motor that finely moves wafer table TB1on stage 171 in the X-axis direction in a state where permanent magnets66A and 66B are each engaged with Y stator 162B. Similarly, permanentmagnets 66A and 66B arranged in wafer table TB2 each constitute a voicecoil motor that finely moves wafer table TB2 on stage 171 in the X-axisdirection in a state (the state in FIG. 9) where permanent magnets 66Aand 66B are each engaged with Y stator 162B, as well as constitute avoice coil motor that finely moves wafer table TB2 on stage 52 in theX-axis direction in a state where permanent magnets 66A and 66B are eachengaged with Y stator 62B.

The position of wafer tables TB1 and TB2 within the XY plane is measuredwith a laser interferometer or other position measuring units (notshown), and the measurement results are sent to a main controller (notshown). In addition, each motor previously described that constituteswafer stage unit 300 operates under the control of the main controller.

The configuration of other parts is the same as the configuration inexposure apparatus 100 of the first embodiment previously described.

In the exposure apparatus of the second embodiment configured in themanner described above, the following processing sequence can beperformed under the control of the main controller.

More specifically, for example, wafer table TB2 (or TB1) that holdswafer W is provided on one of the stages, stage 171. And, in parallelwith detection operation (such as wafer alignment measurement operationby the EGA method) of alignment marks formed on wafer W mounted on wafertable TB2 (or TB1), which is performed below alignment detection systemALG′ while wafer table TB2 (or TB1) is being driven two dimensionally,exposure operation of wafer W held on wafer table TB1 (or TB2) providedon the other stage is also performed by drive unit 50 in thestep-and-scan method described earlier, while wafer table TB1 (or TB2)is being driven.

Then, after the parallel operation has been completed, stage 171 ismoved to a position closest to stage 52 using Y-axis linear motors 176Aand 176B, and the positional relation of both stages 171 and 52 in theX-axis direction is also adjusted so that the position of both stages171 and 52 in the X-axis direction coincides with each other.

Next, wafer table TB1 (or TB2) holding wafer W that has already beenexposed is driven in the −Y direction by the electromagnetic interactionbetween Y movers 60A and 60B and Y stators 62A and 62B arranged in thewafer table. At the same time, wafer table TB2 (or TB1) holding wafer Won which mark detection operation has already been completed is alsodriven in the −Y direction at the same speed as the other stage by theelectromagnetic interaction between Y movers 60A and 60B and Y stators162A and 162B arranged in the wafer table. Accordingly, both wafertables TB1 and TB2 move in the −Y direction while maintaining thepositional relation closest to each other.

Then, when a predetermined amount of time passes after wafer tables TB1and TB2 begin to move in the −Y direction as is described above, Ymovers 60A and 60B arranged in wafer table TB2 (or TB1) holding wafer Won which mark detection operation has already been completed, move intoa state where movers 60A and 60B become engaged simultaneously with Ystators 162A and 162B and Y stators 62A and 62B. This state is shown inFIG. 10.

Then, when wafer tables TB1 and TB2 move from the state in FIG. 10further in the −Y direction by a predetermined distance, Y movers 60Aand 60B arranged in wafer table TB1 (or TB2) holding wafer W that hasalready been exposed reach a position (detaching position) where Ymovers 60A and 60B become completely detached from Y stators 62A and62B. And, just before wafer table TB1 (or TB2) reaches the detachingposition described above, a robot arm (not shown) receives wafer tableTB1 (or TB2), and carries wafer table TB1 (or TB2) to a wafer exchangeposition near alignment detection system ALG′.

At this point, wafer table TB2 (or TB1) holding wafer W on which markdetection operation has already been completed has reached the positionunder hydrostatic pad 32 arranged on the lower end of optical unit PU.And then, wafer table TB2 (or TB1) moves to a position where its entirebody is mounted on stage 52, which completes the wafer table exchangeoperation on stage 52.

As is described above, in the second embodiment, movement of the wafertable holding wafer W that has already been exposed in the −Y directionon stage 52 and the delivery of the wafer table to the robot arm, andthe movement of the wafer table holding wafer W on which mark detectionoperation has already been completed from stage 171 to stage 52 areperformed in parallel. As a consequence, one of the wafer tables islocated constantly under hydrostatic pad 32 directly below projectionoptical system PL, that is, below the optical member (SIL 22 or thefirst segment lens 152 a described earlier) closest to the image planeof the optical members constituting projection optical system PL, andthe state where an immersion area is formed between the wafer table andthe wafer on the wafer table or auxiliary plate 24 is maintained, whichallows the liquid (water) to be held between projection optical systemPL, or in other words, the optical member closest to the image planeconstituting projection optical system PL, and the wafer or auxiliaryplate 24. Accordingly, it becomes possible to keep the liquid (water)from flowing out.

In addition, in the second embodiment, because the exposure operation ofthe wafer on one of the wafer tables and the mark detection operation(and wafer exchange operation) of the wafer on the other wafer table areperformed in parallel, throughput can be improved compared with whenwafer exchange, mark detection operation, and exposure is performedsequentially. In the case the exposure apparatus is equipped with two ormore wafer tables, exposure can be performed on one of the wafer tables,while on another wafer table, drying time may be arranged to completelydry the wafer. In such a case, in order to optimize the throughput, itis desirable to arrange three wafer tables and perform a parallelprocessing sequence of performing exposure operation on the first wafertable, performing alignment operation on the second wafer table, andperforming wafer drying after exposure and wafer exchange operation onthe third wafer table.

In the second embodiment, it is desirable to convert the positionalinformation (array coordinates) of the plurality of shot areas on waferW obtained by the mark detection operation (such as wafer alignmentmeasurement by the EGA method) into information that uses the fiducialmarks on fiducial mark plate FM as a reference. Then, when the waferthat has completed the alignment measurement moves onto stage 52, bymeasuring the relative position of the marks on the reticle and thefiducial marks on fiducial mark plate FM using the reticle alignmentsystem (not shown), the relative position between the reticle and eachshot area on wafer W can be adjusted with high precision to a desiredrelation, even in the case when the wafer table is being moved and thepositional information is difficult to detect continuously.

In addition, as exposure apparatus that are equipped with a plurality oftables, the present invention can also be suitably applied to exposureapparatus disclosed in, for example, Kokai (Japanese Unexamined PatentPublication) Nos. 10-163099 and 10-214783 (corresponding U.S. Pat. Nos.6,341,007, 6,400,441, 6,549,269, and 6,590,634), Kohyo (JapaneseUnexamined Patent Publication) No. 2000-505958 (corresponding U.S. Pat.No. 5,969,441), and U.S. Pat. No. 6,208,407.

In addition, as an exposure apparatus equipped with a plurality oftables, the present invention can also be suitably applied to theexposure apparatus disclosed in, for example, Kokai (Japanese UnexaminedPatent Publication) No. 11-135400 (corresponding InternationalPublication No. WO99/23692).

As long as the national laws in designated states or elected states, towhich this international application is applied, permit, the disclosuresof each of the publications and the corresponding U.S. patents citedabove are fully incorporated herein by reference.

The configuration of hydrostatic pad 32 is not limited to the onesdescribed in each of the embodiments above, and hydrostatic pad 32 mayemploy a configuration such as a hydrostatic pad 32′ shown in FIG. 11A.More specifically, drainage groove 68, water supply groove 70, anddrainage groove 72 may be divided with partition walls that are spacedapart at an equal angle (hereinafter, the section surrounded by thepartition walls is to be referred to as a ‘cell’, and the cells formedin drainage grooves 68 and 72 are to be referred to as ‘drainage cells’and the cells formed in water supply groove 70 are to be referred to as‘water supply cells’).

On the bottom surface of the drainage cells, a through hole 74 thatpenetrate the page surface of FIG. 11A in a right angle direction (theZ-axis direction) is formed in each cell, whereas on the bottom surfaceof the water supply cells formed in water supply groove 70, a throughhole 78 is formed in each cell, and on the bottom surface of thedrainage cells formed in drainage groove 68, a through hole 82 is formedin each cell.

By forming the cells dividing the water supply groove and the drainagegrooves with partition walls, in the case when the pressure of the cellscorresponding to the edge of the wafer changes when hydrostatic pad 32comes into contact with the edge of the wafer, the influence of suchpressure change can be kept from affecting other cells.

In water supply pipes 80 and drainage pipes 84 and 76, connecting tothrough holes 78, 82, and 74, respectively, a stop 79 may be arranged asis shown in FIG. 11B. Also in this case, when a part of the cells comeinto contact with the edge of the wafer, stop 79 can keep the influenceof such pressure change from affecting other cells as much as possible.

In addition, hydrostatic pad 34 on the lower side can employ theconfiguration shown in FIG. 11A, and a stop as in FIG. 11B can bearranged in the water supply pipes and the drainage pipes connecting tohydrostatic pad 34.

In each of the embodiments above, solid immersion lens SIL is employedas the optical element of projection optical system PL closest to theimage plane (wafer W). However, instead of solid immersion lens SIL, alens element composed of quartz or fluorite can be used, or anon-refractive power parallel plane plate can also be used.

In addition, in each of the embodiments above, elastic body 25 isincorporated between auxiliary plate 24 and wafer table TB (TB1, TB2),however, if the gap between hydrostatic pad 32 and its opposing surface(the surface of wafer W, the upper surface of auxiliary plate 24) can beconstantly maintained, elastic body 25 can be omitted.

In each of the embodiments above, ultra pure water (water) is used asthe liquid; however, it is a matter of course that the present inventionis not limited to this. As the liquid, a safe liquid that is chemicallystable and has high transmittance to illumination light IL, such as afluorine-based inert liquid, can be used. As such fluorine-based inertliquid, for example, Florinert (trade name; manufactured by 3M) can beused. The fluorine-based inert liquid is also excellent from the pointof cooling effect. In addition, as the liquid, a liquid which has hightransmittance to illumination light IL and a refractive index as high aspossible, and furthermore, a liquid which is stable against theprojection optical system and the photoresist coated on the surface ofthe wafer (for example, cedarwood oil or the like) can also be used.

In addition, in each of the embodiments above, the case has beendescribed where the path supplying the liquid to the hydrostatic pad (orunder SIL 22) and the path recovering the liquid from the hydrostaticpad are different. However, a configuration that employs the combinationof a circulation path that supplies the liquid recovered from thehydrostatic pad (or under SIL 22) again to the hydrostatic pad (or underSIL 22) and the liquid supply/drainage unit can be employed. In thiscase, in the circulation path, it is desirable to arrange a filter forremoving impurities from the liquid that is collected, in a part of therecovery path.

In each of the embodiments described above, an auxiliary plate isprovided in the periphery of the area where wafer W is mounted on thewafer table; however, in the present invention, there are some caseswhere the exposure apparatus does not necessarily require an auxiliaryplate or a flat plate that has a similar function on table. In thiscase, however, it is preferable to further provide piping on the wafertable for recovering the liquid so that the supplied liquid is notspilled from the wafer table.

In each of the embodiments described above, in the case when the surfaceof the wafer is locally uneven, the surface of the wafer (exposuresurface) and the image plane may be misaligned. Accordingly, in the casewhen the surface of the wafer is expected to be uneven, information onthe unevenness of the wafer can be stored prior to exposure, and duringexposure, the position and the shape of the image plane can be adjustedby performing at least one of moving a part of the lens of theprojection optical system, moving the reticle, and finely adjusting thewavelength of the exposure light.

In each of the embodiments above, as illumination light IL, farultraviolet light such as the ArF excimer laser beam or the KrF excimerlaser beam, or bright lines in the ultraviolet region generated by anultra high-pressure mercury lamp (such as the g-line or the i-line) isused. The present invention, however, is not limited to this, and aharmonic wave (e.g., with a wavelength of 193 nm) may also be used thatis obtained by amplifying a single-wavelength laser beam in the infraredor visible range emitted by a DFB semiconductor laser or fiber laser,with a fiber amplifier doped with, for example, erbium (Er) (or botherbium and ytterbium (Yb)), and by converting the wavelength intoultraviolet light using a nonlinear optical crystal.

In addition, projection optical system PL is not limited to a dioptricsystem, and a catadioptric system may also be used. Furthermore, theprojection magnification is not limited to magnification such as ¼ or ⅕,and the magnification may also be 1/10 or the like.

In each of the embodiments described above, the case has been describedwhere the present invention is applied to a scanning exposure apparatusbased on the step-and-scan method. It is a matter of course, however,that the present invention is not limited to this. More specifically,the present invention can also be suitably applied to a reductionprojection exposure apparatus based on a step-and-repeat method. In thiscase, besides the point that exposure is performed by a scanningexposure method, the exposure apparatus can basically employ thestructure similar to the one described in the first embodiment andobtain the same effect.

The exposure apparatus in each of the embodiments described above can bemade by incorporating the illumination optical system made up of aplurality of lenses, projection unit PU, and hydrostatic pads 32, 34,and the like into the main body of the exposure apparatus, and byattaching the piping to hydrostatic pads 32, 34, and the like. Then,along with the optical adjustment operation, parts such as the reticlestage and the wafer stage made up of multiple mechanical parts are alsoattached to the main body of the exposure apparatus and the wiring andpiping connected. And then, total adjustment (such as electricaladjustment and operation check) is performed, which completes the makingof the exposure apparatus. The exposure apparatus is preferably built ina clean room where conditions such as the temperature and the degree ofcleanliness are controlled.

In addition, in each of the embodiments described above, the case hasbeen described where the present invention is applied to exposureapparatus used for manufacturing semiconductor devices. The presentinvention, however, is not limited to this, and it can be widely appliedto an exposure apparatus for manufacturing liquid crystal displays whichtransfers a liquid crystal display device pattern onto a square shapedglass plate, and to an exposure apparatus for manufacturing thin-filmmagnetic heads, imaging devices, micromachines, organic EL, DNA chips,or the like.

In addition, the present invention can also be suitably applied to anexposure apparatus that transfers a circuit pattern onto a glasssubstrate or a silicon wafer not only when producing microdevices suchas semiconductors, but also when producing a reticle or a mask used inexposure apparatus such as an optical exposure apparatus, an EUVexposure apparatus, an X-ray exposure apparatus, or an electron beamexposure apparatus. Normally, in the exposure apparatus that uses DUV(deep (far) ultraviolet) light or VUV (vacuum ultraviolet) light, ituses a transmittance type reticle, and as the reticle substrate,materials such as silica glass, fluorine-doped silica glass, fluorite,magnesium fluoride, or crystal are used.

Device Manufacturing Method An embodiment is described below of a devicemanufacturing method in the case where the exposure apparatus describedabove is used in a lithographic process.

FIG. 12 shows a flow chart of an example when manufacturing a device(like an IC or an LSI as in a semiconductor chip, a liquid crystalpanel, a CCD, a thin magnetic head, a micromachine, or the like). As isshown in FIG. 12, in step 201 (design step), the function/performancedesign of a device (for example, designing a circuit for a semiconductordevice) is performed, and pattern design to implement such function isperformed. Then, in step 202 (mask manufacturing step), a mask on whichthe designed circuit pattern is formed is manufactured, whereas, in step203 (wafer manufacturing step), a wafer is manufactured using materialssuch as silicon.

Next, in step 204 (wafer processing step), the actual circuit or thelike is formed on the wafer by lithography or the like in a manner whichwill be described later on, using the mask and wafer prepared in steps201 to 203. Then, in step 205 (device assembly step), device assembly isperformed using the wafer processed in step 204. Step 205 includesprocesses such as the dicing process, the bonding process, and thepackaging process (chip encapsulation) when necessary.

Finally, in step 206 (inspection step), tests on operation, durability,and the like are performed on the devices made in step 205. After thesesteps, the devices are completed and shipped out.

FIG. 13 is a flow chart showing a detailed example of step 204 describedabove when manufacturing a semiconductor device. Referring to FIG. 13,in step 211 (oxidation step), the surface of the wafer is oxidized. Instep 212 (CVD step), an insulating film is formed on the wafer surface.In step 213 (electrode formation step), an electrode is formed on thewafer by vapor deposition. In step 214 (ion implantation step), ions areimplanted into the wafer. Steps 211 to 214 described above make up apre-process in each stage of wafer processing, and the necessaryprocessing is chosen and is executed at each stage.

When the above pre-process is completed in each stage of waferprocessing, a post-process is executed in the manner described below. Inthis post-process, first, in step 215 (resist formation step), the waferis coated with a photosensitive agent. Next, in step 216 (exposurestep), the circuit pattern on the mask is transferred onto the wafer bythe exposure apparatus and the exposure method described above. And, instep 217 (development step), the wafer that has been exposed isdeveloped. Then, in step 218 (etching step), an exposed member of anarea other than the area where the resist remains is removed by etching.Finally, in step 219 (resist removing step), when etching is completed,the resist that is no longer necessary is removed.

By repeatedly performing such preprocess and post-process, multiplecircuit patterns are formed on the wafer.

When the device manufacturing method of the embodiment described so faris used, because the exposure apparatus described in each of theembodiments above is used in the exposure process (step 216), thepattern of the reticle can be transferred on the wafer with goodaccuracy. As a consequence, the productivity (including the yield) ofhighly integrated microdevices can be improved.

While the above-described embodiments of the present invention are thepresently preferred embodiments thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiments without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

1. A lithographic apparatus comprising: a measuring system that measurescharacteristics of substrates in a first area of the apparatus; aprojection system that projects a patterned radiation beam onto asubstrate in a second area of the apparatus; a liquid confinement systemthat at least partly confines liquid in a space between the projectionsystem and the substrate; at least two substrate stages each of whichholds a substrate; and a positioning system that moves the stagesbetween the first area and the second area, and during exposure,positions one of the stages holding a substrate in the second area onthe basis of at least one measured characteristic of that substrate;wherein the stages are positionable so as to be close to or in contactwith each other in order to perform a simultaneous movement of thestages to bring the lithographic apparatus from a first state in whichthe liquid is confined between a first substrate held by a first stageof the substrate stages and the projection system, to a second state inwhich the liquid is confined between a second substrate held by a secondstage of the substrate stages and the projection system, such thatduring the simultaneous movement the liquid is essentially confinedwithin the space in contact with the projection system.
 2. Thelithographic apparatus according to claim 1, wherein each of the firststage and the second stage has a side surface which cooperates with aside surface of another stage during the simultaneous movement.
 3. Thelithographic apparatus according to claim 2, wherein each of the sidesurfaces comprises an essentially planar surface.
 4. The lithographicapparatus according to claim 2, wherein the positioning system positionsthe respective stages during the simultaneous movement such that theirrespective side surfaces remain at an essentially mutual constantspacing.
 5. A lithographic product with a lithographic apparatusaccording to claim
 1. 6. A manufacturing method of manufacturing alithographic apparatus, the method comprising: providing a measuringsystem that measures characteristics of substrates in a first area ofthe apparatus; providing a projection system that projects a patternedradiation beam onto a substrate in a second area of the apparatus;providing a liquid confinement system that at least partly confinesliquid in a space between the projection system and the substrate;providing at least two substrate stages each of which holds a substrate,the substrate stages being positionable so as to be close to or incontact with each other in order to perform a simultaneous movement ofthe stages to bring the lithographic apparatus from a first state inwhich the liquid is confined between a first substrate held by a firststage of the substrate stages and the projection system, to a secondstate in which the liquid is confined between a second substrate held bya second stage of the substrate stages and the projection system, suchthat during the simultaneous movement the liquid is essentially confinedwithin the space in contact with the projection system; and providing apositioning system that moves the stages between the first area and thesecond area, and during exposure, positions one of the stages holding asubstrate in the second area on the basis of at least one measuredcharacteristic of that substrate.
 7. An exposure method, comprising:moving at least two substrate stages each of which holds a substratebetween a first area where measurement of characteristics of substratesis performed and a second area where a patterned radiation beam isprojected from a projection system onto a substrate, and duringexposure, positioning one of the stages holding a substrate in thesecond area on the basis of at least one measured characteristic of thatsubstrate; and positioning the stages so as to be close to or in contactwith each other in order to perform a simultaneous movement of thestages to bring the lithographic apparatus from a first state in whichthe liquid is confined between a first substrate held by a first stageof the substrate stages and the projection system, to a second state inwhich the liquid is confined between a second substrate held by a secondstage of the substrate stages and the projection system, such that theliquid is essentially confined within the space in contact with theprojection system.
 8. The exposure method according to claim 7, whereineach of the first stage and the second stage has a side surface whichcooperates with a side surface of another stage during the simultaneousmovement.
 9. The exposure method according to claim 8, wherein each ofthe side surfaces comprises an essentially planar surface.
 10. Theexposure method according to claim 7, wherein during the simultaneousmovement, the respective stages are positioned such that theirrespective side surfaces remain at an essentially mutual constantspacing.
 11. A device manufacturing method, comprising: exposing asubstrate by using the exposure method according to claim 7; anddeveloping the substrate that has been exposed.